Myological correlates of prosimian leaping

Area of Science:

• Primate Anatomy
• Locomotor Biomechanics
• Functional Morphology

Background:

• Skeletal adaptations for primate vertical clinging and leaping are well-documented.
• Myological data for primate locomotor groups, particularly leapers, is scarce.
• Understanding muscle mass distribution is crucial for inferring locomotor capabilities.

Purpose of the Study:

• To provide relative hindlimb muscle mass data for four prosimian leapers (indriids, tarsiers, galagos).
• To compare muscle mass distribution with locomotor kinematics and body mass.
• To investigate the myological correlates of vertical clinging and leaping behavior.

Main Methods:

• Determined wet weights of hindlimb muscles (excluding intrinsic foot muscles) in four prosimian leapers.
• Collected comparative muscle weight data for an arboreal quadruped (Varecia) and previously unpublished monkey data.
• Analyzed relative muscle mass distribution related to hip, knee, and ankle joint extensors.

Main Results:

• Specialized leapers exhibit a predominance of hindlimb extensor muscles.
• Indriids show larger hip extensors, while galagos and tarsiers have larger ankle plantarflexors, correlating with kinematic differences.
• The quadriceps femoris muscle is overwhelmingly dominant in leapers, suggesting power transfer from the knee.

Conclusions:

• Hindlimb muscle mass distribution in primates is strongly linked to leaping kinematics and locomotor specialization.
• Quadrupedal primates show greater hip extensor musculature, constrained by swing phase requirements.
• Muscle mass scaling with body mass suggests larger leapers have reduced propulsive force per unit weight.